Generally speaking, to make a diagnosis of a cerebral infarction, images that are obtained by performing, for example, Magnetic Resonance Imaging (MRI), Computed Tomography (CT), Single Photon Emission Computed Tomography (SPECT), and Positron Emission Tomography (PET) are used. Unless the circulation in an infarction site is resumed within three hours of an onset, the damage to the brain becomes significant, and part of the body functions of the patient may be lost or the brain damage may result in death.
One of the techniques that are known to be used for treating a lesion is to insert a catheter up to the lesion while viewing an X-ray transmission image. This technique is called an intervention. Examples of intervention treatments that can be applied to the blood vessels that have a direct impact on the head include a treatment by which a catheter is put through a stenosis site in the neck, before the balloon provided around the catheter is blown up so as to expand the stenosis site, and a treatment for a cerebral aneurysm by which a catheter is advanced to a closer end of the cerebral aneurysm, and the aneurysm is filled with a coil ejected from a tip of the catheter, so as to prevent the blood streams from entering the aneurysm. During these treatments, some of the plaques adhering to a blood clot or a stenosis site may flow toward the periphery and may block a peripheral blood vessel so as to cause a cerebral infarction. If such an infarction has occurred in a relatively large blood vessel, it is possible to recognize the occurrence of the infarction during a check-up imaging examination that is performed after the intervention treatment. However, in the case where an infarction has occurred in a small blood vessel, it is difficult, in many cases, to recognize the occurrence of the infarction during a check-up imaging examination. In those situations, according to a currently-used workflow, it is determined whether an infarction has occurred by performing a CT examination, an MRI examination, or the like when three hours or one day has passed since the completion of the intervention treatment. According to this workflow, however, it is extremely difficult to resume the circulation in the infarction site within three hours of an onset.
To cope with this problem, a function has recently been proposed with which it is possible to check the manner in which blood is perfused by employing an X-ray angiography apparatus used for performing intervention treatments. When this function is used, images are taken while a C-arm is rotated around a patient at a high speed before and after a contrast media is injected into the patient. A three-dimensional image indicating an opacification degree of the contrast media is generated by reconstructing an image while using a subtraction image between the images taken before and after the injection of the contrast media, and also, a three-dimensional image indicating a body structure of the patient is generated from the image taken before the injection. After that, an area that has a CT value corresponding to the brain tissue is extracted from the three-dimensional image indicating the body structure. Further, by eliminating the areas other than the extracted area from the three-dimensional image indicating the opacification degree of the contract agent, it is possible to extract only the opacification degree of the contrast media in the brain tissue. There is a possibility that a part of the brain tissue that exhibits a low degree of opacification from the contrast media may be an infarction site. It is also possible to determine that the parts that exhibit a high degree of opacification from the contrast media have normal bloodstreams. It should be noted, however, that this imaging process is not supposed to be performed as a routine. Thus, the amount of contrast media used in the imaging process and the radiation exposure dose for the patient cause an additional burden upon the patient. In particular, according to this method, it is necessary to visualize the veins using a contrast media, the capillary vessels, and the arteries altogether, and the amount of the contrast media being used is very large.